Show us your favorite perf gauge

I have three perforation gauges. All were "good customer" gifts. The one on the left is from Yvert & Tellier (I actually got two of those), and the reverse side has additional perforation ratings 13 to 18. It's just laminated paper. The one in the middle is clear plastic, and I got it at a stamp shop in Trenton, NJ. It's nice because it allows for gauge measurements with 0.1 accuracy, which is sometimes necessary, especially for die-cut US issues. The one of the right is from the Centre Philatélique de Québec. I don't know if they are still in business, but they were my main source of stamps on approval during the 1980s and 1990s when I lived in Montreal and then during my college years in Texas. It's just light cardboard paper, printed on a single side, and shows its grand age. I've had to tape it back a few times and it was my only perforation gauge for many years. The paper ones I often use as page-markers in my catalogs (especially while navigating between various sections) while the clear plastic Scott one is by my side on my desk at all times. Even though my aging eyes are not always happy with the clear plastic, it does have the advantage that you can choose to put the stamp either over or under it when measuring, which is sometimes handy, especially if the stamp is on piece. It works, as long as you have a light source handy, which is where my backlit magnifying glass comes in.

I've had the small metal gauge for over 20 years. These days my favorite is the one next to it (Phila Combi Box).

I'll go in a slightly different direction. I use these two.

If you haven't let the publishers know, you should drop them a note. That's a common Java error, and it's usually pretty easy to fix.

I love this one.

Regarding roto gage, anyone actually come across or use this gizmo?

I have one and as I stated, I love it. JeffS

One lays the stamp on the perforation lines and turns the knob until the right perfs line up with the stamp, and the magnifying glass is adjustable.

I get good results only with a transparent ruler.
I measure the distance over 10 teeth (this reduces the effect of the reading error) – 14.3 mm.
The stamp is Scott #22, 1949, Bahawalpur, perforation 14.
I calculate the perforation by dividing 20mm to 1.43mm and the result is 13.98.
A different reading, for example 14.2 or 14.4 mm leads to a perforation calculated 14.08 or 13.89 close enough to the value 14.

Although I have a metal Buxton Multi-Gage and the Sonic Imagery Labs Multi-Gauge, my day-to-day preference is this Showgard Vidiforms gauge.